1. Technical Field
Illustrative embodiments described in this patent specification generally relate to a sheet feeding device including a sheet feed cassette to feed a recording medium, and an image forming apparatus including the sheet feeding device.
2. Description of the Related Art
Related-art image forming apparatuses, such as copiers, facsimile machines, printers, or multifunction devices having two or more of copying, printing, scanning, and facsimile functions, typically form a toner image on a recording medium (e.g., a sheet) according to image data using an electrophotographic method. In such a method, for example, a charger charges a surface of a latent image bearing member (e.g., a photoconductor); an irradiating device emits a light beam onto the charged surface of the photoconductor to form an electrostatic latent image on the photoconductor according to the image data; a developing device develops the electrostatic latent image with a developer (e.g., toner) to form a toner image on the photoconductor; a transfer device transfers the toner image formed on the photoconductor onto a sheet; and a fixing device applies heat and pressure to the sheet bearing the toner image to fix the toner image onto the sheet. The sheet bearing the fixed toner image is then discharged from the image forming apparatus.
The image forming apparatuses further include a sheet feeding device including a sheet feed cassette to feed a recording medium such as a sheet to the image forming parts of the apparatuses.
One example of the sheet feeding device includes a configuration designed to detect a size of a sheet stored in a sheet feed cassette without increasing either a size of the sheet feed cassette and a force required to operate an end fence member and without damaging a size detection means. The sheet feed cassette of such a sheet feeding device includes the end fence serving as a rear edge restriction member to restrict a position of a rear edge of the sheet stored in the sheet feed cassette in a direction of sheet feed, and the size detection means having a groove so that the end fence is moved in the direction of sheet feed. The size detection means is swingably provided on a bottom plate of the sheet feed cassette. A pivot of the size detection means is positioned at an edge of the size detection means in a direction of sheet feed, and a free edge thereof is positioned at the other edge where the end fence is moved. A length of the size detection means is extended such that the free edge of the size detection means is positioned at an edge in a direction opposite the direction of sheet feed, and a size detection part is provided at that edge in the direction opposite the direction of sheet feed.
However, in the above-described sheet feeding device, a space for installing the size detection part is required in the direction opposite the direction of sheet feed. Consequently, a size of the sheet feeding device is increased. Further, because a position of the free edge of the size detection means contacting the size detection part is not changed even when the sheet feed cassette is contracted, the size of the sheet feeding device in the direction of sheet feed may not be reduced.
Published unexamined Japanese Utility Model Application No. H06-001349 discloses a sheet feeding device including microswitches that detect a size of a sheet stored in a sheet feed cassette capable of storing sheets having a variety of different sizes. In order to reduce the number of the microswitches, rollers are provided at an edge of a restriction plate that restricts a position of a rear edge of the sheet. Further, linear cam plates are rotatably provided at positions corresponding to the rollers. Each of the linear cam plates is rotated outwardly, and an external protrusion is formed outside of each of the linear cam plates. The microswitches are provided at positions opposite the external protrusions.
However, in the sheet feeding device described above, because a size detection part is positioned in the direction of sheet feed, a space for installing the size detection part in the sheet feeding device is required in the direction of sheet feed, causing an increase in a size of the sheet feeding device.
In yet another approach, a sheet feeding device in which a size detection cam operating in conjunction with an end fence, and a size detection part provided on a lateral surface side of a sheet feed cassette are used for size detection has been proposed.
However, although the size detection part is provided on the lateral surface side of the sheet feed cassette in the above-described sheet feeding device, the sheet feed cassette is not configured to be extended or contracted in the direction of sheet feed. Consequently, an installation area for the sheet feeding device may be larger than the maximum size of the sheet stored in the sheet feed cassette.